CN1724430A - Process for protecting surface of high temp. titanium alloy - Google Patents
Process for protecting surface of high temp. titanium alloy Download PDFInfo
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- CN1724430A CN1724430A CNA2005100467202A CN200510046720A CN1724430A CN 1724430 A CN1724430 A CN 1724430A CN A2005100467202 A CNA2005100467202 A CN A2005100467202A CN 200510046720 A CN200510046720 A CN 200510046720A CN 1724430 A CN1724430 A CN 1724430A
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Abstract
A surface protecting method for refractory Ti-alloy includes such steps as preparing a refractory enamel proportionally containing Al, Si, Ca, Zn, Zr, Na, Mg, Ce and O, coating it on the surface of Ti-alloy by electrophoresis, and sintering.
Description
Technical field:
The present invention relates to the high temperature protection technology of titanium and alloy thereof, a kind of enamel powder for electrophoresis coating is provided especially, its preparation method, and prepare the surfacecti proteon that high-temperature protection coating is used for high-temperature titanium alloy with this enamel powder.
Background technology:
Because of titanium and alloy thereof active big; very easily oxidation at high temperature; thereby one of the important factor that influences high-temperature titanium alloy work-ing life is the raising along with use temperature; oxidizing reaction faster takes place in air ambient; alloy surface can not form the oxide compound with provide protection; a large amount of Sauerstoffatom that made in the matrix below the oxide compound solid solution, thus form the fragility oxygen-rich layer, grievous injury the mechanical property of alloy.Therefore, the research of high-temperature titanium alloy antioxidant property and high-temperature protection coating becomes one of key problem in technology of alloy application.People turn to attention at alloy surface coating oxidation-resistant coating when making great efforts to improve the high-temperature titanium alloy performance, to increase the ability of alloy opposing environmental disruption.The Russia expert thinks that if without high-temperature oxidation resistant coating, the long term operation temperature Gonna breakthrough of titanium alloy is unlikely for 600～650 ℃.Therefore, except that metallurgy factor, the research of high-temperature oxidation resistant coating is very urgent.In China, in nearly more than 20 years time, people have used many technology, as bury technology such as the method for oozing, slurry process, galvanic deposit, plasma spraying, at high-temperature titanium alloy surface coating as Al, Pt, NiCr, Si
3N
4, coated material such as MCrAlY, but all have certain defective, do not realize real application, illustrate that more deep research also need be carried out in the protection field of high-temperature titanium alloy.
High-temperature titanium alloy is that the titanium alloy field is the most active, an of paramount importance branch, however the very hardships of its development course.Use temperature rises to 550 ℃ of present times of having experienced about 40 years by early stage 400 ℃, raise 3.75 ℃ every year on average, thereby developing effective, practical surface protection coating technology is a problem demanding prompt solution.Enamel coating has that oxidation-resistance is strong, solidity to corrosion good and higher chemical stability, and the coefficient of expansion can regulate by composition and make it near the high-temperature titanium alloy matrix, is a kind of excellent high-temperature oxidation resistant coating material.
Enamel coating glazing mode generally adopts the method for spraying slip and dip-coating at present, and it is thicker to preset enamel layer, very easily produces the drawback at plump edge.
Summary of the invention:
The object of the present invention is to provide a kind of enamel powder for electrophoresis coating, this enamel powder can be used for electrophoresis precoating enamel coating, thereby makes enamel coating thinner, more even, and antioxidant property does not reduce.
The present invention also aims to provide a kind of process for protecting surface of high-temperature titanium alloy, this method is by at the uniform enamel coating of surface-coated one deck thin layer of high-temperature titanium alloy, makes the high-temperature titanium alloy material pieces itself have stronger oxidation-resistance, good solidity to corrosion and higher chemical stability.
The present invention at first provides a kind of enamel powder for electrophoresis coating, it is characterized in that the chemical constitution of described enamel powder is weight percent:
Al
2O
3 6.5～10.2；
ZrO
2 2.7～4.2；
ZnO 5.3～8.9；
B
2O
3 2.7～4.3；
CaO 1.9～3.8；
Na
2O 1.9～3.6；
Rare earth oxide 1.0-2.0;
Mg(NO
3)
2 2.0～5.6；
ZrSiO
4 12.2～15.8；
Na
2B
4O
7 5.2～8.0
SiO
2And other impurity surplus.
In the enamel powder for electrophoresis coating of the present invention, preferred composition is Al
2O
32.1-3.5; Mg (NO
3)
22.0-3.6; ZrSiO
42.0-14.5.
In the enamel powder for electrophoresis coating of the present invention, rare earth oxide is preferably CeO
2
In the enamel powder for electrophoresis coating of the present invention, powder particles is at 150-350nm.
The present invention also provides the preparation method of above-mentioned electrophoresis precoating enamel coating with the enamel powder, it is characterized in that: the powder of described proportioning is adopted the dehydrated alcohol wet ball grinding in planetary ball mill, concentration is 485g/L～590g/L, rotating speed is 240-325r/min, the powder slurry accounts for 45%～67%Wt% of ball mill loading packet, big ball in the mechanical milling process: big ball: middle ball=1: 2.8～3.2: 4.8～5.2 mass ratioes.
Enamel composition of the present invention is mainly based on oxide compound, adds to add thing after multiple in common enamel powder, thereby changed traditional enamel coating glazing process and firing process.Added a certain amount of metallic salt material to replace oxide compound, as Mg (NO
3)
2Replace MgO, ZrSiO
4Replace SiO
2Deng.The adding of metallic salt has increased the ionic concn of suspension effectively, thereby makes the oxide compound in the enamel can the absorption band electron ion, produces certain reactive force each other, keeps stable suspended state.Evidence, Mg (NO
3)
2Improve the electroconductibility of electrophoresis liquid, and increased charged ion content in the electrophoresis liquid greatly, strengthened the stability of electrophoresis liquid.Find Mg (NO through test of many times
3)
2Add-on should be at 2.0～5.6Wt%, is best with 2.0-3.6, and add-on is low excessively, the directed swimming ability of electrophoresis liquid a little less than, the enamel sedimentation rate is slow, sedimentation effect is lower.Add-on is too high, and the electrophoretic deposition excessive velocities presets enamel layer and is easy to produce pore and crackle, to the sintering process generation adverse influence of enamel coating.Na
2B
4O
7Be mainly used to improve the suspension of swimming liquid, avoid the porcelain glaze powder precipitation.ZrSiO
4Can improve the heat resistance of enamel coating, simultaneously ZrSiO
4Make easier generation chemical reaction in the enamel sintering process, improve coating and high base strength.
Rare earth metal comprises group of the lanthanides and scandium (Sc) and yttrium 17 kinds of elements such as (Y).Be widely used in various fields such as metallurgy, chemical industry, optics, magnetics at present.The rare earth element reserves of China account for more than 80% of global total amount, and the action value of therefore giving full play to rare earth element is great.Because its atomic radius of rare earth element and ionic radius are much larger than common metal ion; Has unusual active chemical property; can generate high stable compound and intermetallic compound with hydrogen, oxygen, nitrogen and many nonmetal, metals and compound effects thereof; and strong oxidation-reduction quality is arranged, have the special propertys such as ability that can absorb a large amount of gases simultaneously.In materials such as mmaterial alloying and matrix material, many successful application have all been obtained.In addition, the research of adding rare earth element and application also more and more cause people's attention in surface-treated layer.
Rare earth because it has special electronic structure, thereby makes it have many special performances.Rare earth is as a kind of interpolation composition, and the effect that is showed has caused numerous workers' interest, and shows in a lot of fields.The mode that rare earths material adds with mill makes an addition in the enamel, helps the reduction of enamel firing temperature, and the improvement of glaze slip suspension property improves glossiness, simultaneously the enamelled performance is also had very big influence.Help the reduction of enamel firing temperature, improve the glossiness of coatingsurface, and can in specific mineral composition, be ground into pigment, the enamelled performance is produced wholesome effect through high temperature sintering.The general natural clay that adopts is made suspension agent in the common enamel glaze slip, the refractory temperature height of clay, and the composition fluctuation of mineral is big gives and reduces firing temperature, improves application of slip performance and improve the quality of products and brought many difficulties.And adopt the rare earth substitute for clay as suspension agent, can improve these performances: (1) reduces firing temperature; (2) improve enamel glaze slip rheological property; (3) improve porcelain facing glossiness and levelling property.
Rare earth adds the various physicalies that will have influence on enamel in the enamel, as application of slip performance, glossiness etc.The adding mode difference of rare earth has different influences to enamel, wherein fashionable enamel is had bigger influence when rare earth adds with the mill add mode.When temperature was lower than the rare earth fusing point, mill added rare earth and can improve heat-resisting acute degeneration of enamelled and shock strength, and does not have obvious influence for chemical stability.Why rare earth can improve the heat-resisting acute degeneration of enamelled, is because rare earth skewness in enamel makes enamelled differential expansion coefficient that certain difference be arranged, and a buffering course is arranged when being subjected to the cold and hot sudden turn of events.
Add rare earth oxide in the enamel material and cause structure refinement easily in sintering process, rare earth is to become the crystalline nucleating agent because rare earth forms refractory oxide to the influence of tissue, thereby makes the crystal refinement.Rare earth is that surface active element tends to surface arrangement, is easy to generate wicking action between rare earth and the enamel, makes fusion phase flow direction pore place effectively fill the space at the enamel fusing initial stage.The present inventor adopts multiple rare earth oxide to carry out test of many times, finds that mill adds CeO
2Effect stability, CeO
2Add-on be the best with 1.0～2.0Wt%, add-on is low excessively, its effect is very unobvious, add-on is too high, the enamel film process is accelerated, the film forming levelling property variation of sintering process enamel is difficult to adapt to the requirement of actual condition.This research adds CeO
2Reduced the viscosity of electrophoresis liquid, strengthened flowability, made easier the overflowing of gas in the swimming liquid, thereby reduced the porosity of enamel coating, antioxidant property, Corrosion Protection and other mechanical property to enamel coating all will produce desirable influence like this.
Mechanical milling process is remarkable to the electrophoresis experiment influential effect.The ball milling effect changes with the change of powder concn, and when hanging down the powder slurry concentration scope, grinding efficiency is little with change in concentration; Increase ball milling effect along with concentration in the higher concentration scope obviously improves, if but excessive concentration powder regional area is easy to generate higher yielding stress, and make the ball milling speed in this zone lower, the processing power of grinding machine will decline to a great extent.The concentration that adopts in the experiment is 485g/L～590g/L.Ball mill should have an enough big rotating speed to make spherolite can cling ball grinder fully, and produces sufficient centrifugal force the enamel powder is ground.Rotating speed is crossed slowly and can not fully be ground, and the too fast powder slurry of rotating speed separates with abrading-ball, reduces grinding effect.The rotating speed that adopts among the present invention is 240-325r/min.
In mechanical milling process, when abrading-ball rotated at ball mill, every layer of abrading-ball respectively do not collide with other layer ball is chaotic by the route motion of oneself, is best loading capacity like this.Total abrading-ball amount should be that grinding machine center to abrading-ball the horizontal plane is 0.16R (R is the grinding machine internal diameter) when ball mill is static.As for the ball mill total raw material amount of packing into, should slightly exceed ball material such as Fig. 2.Abrasive material and powder slurry accounts for 45%～67% of loading packet altogether and is advisable among the present invention.Abrading-ball should have rational size, shape, proportion and enough hardness, and piles up and want closely.The present invention adopts agate ball to make the abrasive material ball, can fully overcome enamel powder high rigidity, nonabradable characteristics.Wherein big ball: middle ball: bead=1: 3: 3.5 (mass ratio).For the enamel powder, it is most important that can mechanical milling process form steady suspension to it.In the mechanical milling process between ethanol and the enamel powder thorough mixing wetting, combine together, thereby guarantee the layering situation not occur in the electrophoresis process suspension.
The present invention provides a kind of process for protecting surface of high-temperature titanium alloy in addition, it is characterized in that: at surface preparation one deck high-temperature oxidation resistant enamel coating of high-temperature titanium alloy;
Coat-thickness is: 15-70 μ m
Chemical constitution is (Wt%): Al:2.6-4.2; Si:20.7-29.8; Ca:1.9-2.4; Zn:1.2-2.0; Zr:2.6-3.7; Na:0.4-1.1; Mg:0.4-0.9; Ce:0.6-1.2; O and impurity surplus
In the process for protecting surface of high-temperature titanium alloy of the present invention, the preparation technology of described high-temperature oxidation resistant enamel coating is:
---electrophoresis precoating enamel coating,
The chemical constitution of enamel powder is that weight percent is:
Al
2O
3 6.5～10.2；
ZrO
2 2.7～4.2；
ZnO 5.3～8.9；
B
2O
3 2.7～4.3；
CaO 1.9～3.8；
Na
2O 1.9～3.6；
Rare earth oxide 1.0-2.0;
Mg(NO
3)
2 2.0～5.6；
ZrSiO
4 12.2～15.8；
Na
2B
4O
7 5.2～8.0
SiO
2And other impurity surplus;
With ethanol is that dispersion agent prepares slip, pulp density 150-200g/L;
Electrophoretic voltage 20-30V;
Depositing time 3-5s;
Interpole gap 1.5-2.5cm gently stirs or does not stir;
---sintering:
Temperature 850-880 ℃, soaking time 20-40min.
In the process for protecting surface of high-temperature titanium alloy of the present invention, the preferred composition of enamel powder is Al
2O
32.1-3.5; Mg (NO
3)
22.0-3.6; ZrSiO
42.0-14.5.Rare earth oxide is preferably CeO
2
Electrophoretic deposition is to be united by electrophoresis and two processes of deposition to form, and wherein slower step becomes the committed step of control enamel sedimentation rate.The key of this technology is the stable colloid plating bath of processability.So-called colloid is a kind of dispersion system between true solution and thick solution, and its dispersed particle radius is between 10
-9M～10
-7Between the m.Want sedimentary microparticulate in inorganic or organic dispersion medium institute with certain method, obtain the suspension of stable performance, promptly can be used as electrophoretic deposition.Because suspension is a thermodynamic unstable system, particulate has coalescent mutually and reduces the trend of its surface-area, therefore will obtain steady suspension and must make microparticle surfaces charged.Particulate with interface that polarizable medium such as water, ethanol, Virahol etc. contact on effects such as ionization, ionic adsorption or ion dissolving take place, make ion surface charged.
Using water compositing dispersion medium still is that organism is made dispersion medium, very big to the performance impact of electrophoretic deposition layer.Because the decomposition voltage of water is lower, therefore no matter use constant voltage mode or constant current mode, voltage that is applied or electric current all can not be too big, otherwise the settled layer density that obtains is less or degree of uniformity is relatively poor, even can not get complete settled layer.The settled layer that uses non-aqueous media to obtain is fine and close relatively.The present invention has examined or check the influence to stability of suspension of water and ethanol two media dispersion agent.
Solvent is used for adjusting the viscosity of coating in electrophoretic deposition process, make coating form even continuous thin film, and subsequently, solvent is evaporated in the drying process of filming in the air and removes automatically.Ethanol is polar molecule, and each polar molecule surface in the as easy as rolling off a log wetting enamel slip makes its dispersion.Comparatively speaking, the polar molecule in the more difficult wetting enamel powdered frit of water, with this as dispersion medium, can cause the layering of suspension, make its stability decreases, and the electrolytic potential of water is lower, produced gas by electrolysis easily in the electrophoresis process, thereby influence the surface quality of coating.Therefore, adopt dehydrated alcohol as dispersion medium among the present invention.
The ionization of electrophoretic deposition process and ethanolic soln is closely related.The process of this test is described with the ionization of ethanol molecule below.It is generally acknowledged under External Electrical Field why suspension can produce deposition is that its result has been equivalent to reduce near the zeta-potential the electrode because electrolyte concentration increases near the electrode, thereby make the particle flocculation.C
2H
5Ionization reaction at first takes place in OH in suspension:
The equilibrium constant of the above-mentioned dissociation reaction in the suspension system is under certain condition:
K=[H
+] [C
2H
5O
-]/[C
2H
5OH] near negative electrode, H
+Concentration significantly increase, in order to safeguard balance, C
2H
5The concentration of OH must increase or reduce C
2H
5O
-And C
2H
5O
-Constitute electric double layer particle (C
2H
5O)
- Two, near electrostatic double layer particle (C
2H
5O)
- TwoThe C on surface
2H
5O
-And C
2H
5The bonding force of OH molecule is stronger.Far away from the electrostatic double layer particle surface, the bonding force of particle reduces.(C
2H
5O)
- TwoCan react it and H with positive ion
+In conjunction with having increased C in the system
2H
5The concentration of OH has reduced H simultaneously
+And C
2H
5O
-Concentration, that is:
。C
2H
5OH produces diffusion and does not deposit to bulk suspension along its concentration gradient direction, and K remains constant like this.Since this result, the electrostatic double layer attenuation around the particle, and so enter enough near that the particle of electrostatic double layer just can lean on, consequently Van der Waals'attractive force is occupied an leading position, thereby deposits.Electrophoretic deposition process as shown in Figure 1.
The tributary electric current plays the effect of motivating force to suspension in the electrophoresis process, makes particle can overcome each other energy barrier, and Fig. 2 is the relation of particle interphase interaction power and grain spacing.Total DLVO reactive force (F between particle when without any applied external force
T) provide by solid line among the figure.When adding a DC electric field, particle A at first arrived matrix surface and particle B close gradually, this moment, the electric field that applies provided electrophoretic force (F to particle B
E), make it produce electrophoretic velocity and also can overcome the viscosity resistance of electrophoresis liquid and the repulsive force between the particle, thereby arrive matrix surface.Horizontal dotted line is represented electrophoretic force F among the figure
E, interparticle force has been adjusted in the existence of electrophoretic force effectively, has promptly produced actual interaction force F
M(F
M=F
T+ F
E), as dotted line crooked among Fig. 2.
From energy point of view, in the electrophoresis process, particle deposition need overcome the potential energy barrier (E of certain altitude
b).After applying certain voltage on the electrode, directed moving takes place in charged particulate in the suspension, if first porcelain glaze powder particulate preferentially arrives electrode surface, at this moment next porcelain glaze powder particulate to electrode surface or semi-permeable membranes near the time, will be subjected to the repulsion force of enamel particles A.The voltage that applies can overcome interparticle barrier height (E
B) (as shown in Figure 3), thereby obtain enamel electrophoretic deposition layer; If the voltage that applies is too little, can not cross interparticle barrier height (E
B), then substrate surface does not have the enamel settled layer to form; Simultaneously, if apply on the too big then electrode of voltage the performance that other electrochemical reaction is destroyed the enamel settled layer may take place.
The present inventor examines or check the electrophoresis liquid of different powder slurry concentrations by experiment.Found that, when powder slurry concentration during more than or equal to 150g/L, the electrophoretic deposition layer adhesivity that is obtained is big, no unconsolidated formation on it, the settled layer densification, deposit thickness is also more even when depositing at short notice, but when too high (when powder slurry concentration reaches 350g/L) even can not form the electrophoretic deposition coating.This is because powder slurry concentration is too high, therefore the content of electrophoresis liquid intermediate ion is reduced relatively, reduce the effectively charged of enamel powdered frit, even make and contain too much free enamel powder in the electrophoresis liquid, the orientation of enamel particle moves and is obstructed when causing electrophoresis, thereby electrophoretic deposition process is obstructed.If powder slurry concentration is low excessively, then coating attenuation, coulombic efficiency (can deposit the milligram number of dry deposition film by 1 coulomb electric charge) reduction in mg/c, even can not form continuous, even, fine and close enamel coating during electrophoresis.
When finding also that by test electrophoresis concentration is high slightly, can effectively suppress the corner effect that electrophoresis brings,, make particle at first be deposited on corner areas easily, cause the coat-thickness inequality owing to be in the sample conducting process by the edge discharge.When suitably improving powder slurry concentration, assemble a large amount of particles around the sample, particle is trending towards being subjected in the process of corner the obstruction of a large amount of particles when energising, thereby the in-plant local deposition of easier selection, thereby makes coating more even.
Since drive particle directed move and electrode on redox reaction takes place all needs certain voltage, therefore have only when voltage greater than a certain value, porcelain glaze powder just can be deposited on substrate surface, this current potential is called critical potential.By dlvo theory as can be known, under different situations, exist between the various particles attract each other can and repulsive energy mutually, the relation curve of total interaction energy E between particle (comprise repulsive energy and attract can) and its distance D is as shown in Figure 3.Particle deposition need overcome the potential energy barrier E of certain altitude as we can see from the figure
BAfter applying certain voltage on the electrode, directed moving takes place in charged enamel particulate in the suspension, and the enamel particles B is in the repulsion force that will be subjected to the enamel particles A when electrode surface is close when preferentially arriving electrode surface as if the enamel particles A.If the voltage that applies can overcome interparticle barrier height (E
B) then can access enamel electrophoretic deposition layer.When the voltage that applies is too little, can not cross interparticle barrier height (E
B), then substrate surface does not have the enamel settled layer to form.Simultaneously, it is excessive to apply voltage, then on the electrode other electrochemical reaction may take place, and destroys the performance of enamel settled layer.
Experiment finds that there is certain influence the electrophoretic deposition time to the settled layer quality.The deposition of glaze is directly proportional with the energising amount.Before coating reaches certain thickness, the increase of coat-thickness and the time relation of being in line.But reach after the certain thickness, the increase of coat-thickness is slowed down, so as long as guarantee certain electrophoresis time, even pole distance and electrophoretic voltage are variant, also can obtain identical coat-thickness.
The performance of electrophoretic deposition layer of the present invention not only is decided by voltage, dispersion medium, electrophoresis liquid powder slurry concentration and electrophoresis time, but also is subjected to the influence of factors such as stirring state and interpole gap.
In the electrophoretic deposition process, under quick condition of stirring, settled layer washes away down at fluidic, causes coat-thickness seriously inhomogeneous, the edge of substrate and near thickness very little or do not have a deposition, then become bulk or island in the central authorities of substrate.Under extreme case, even there is not the deposition generation on the whole substrate.Stirring at a slow speed or not under the condition of stirring, deposit thickness is even.As seen, overgenerous stirring has the influence of unfavorable or damageability in the deposition process to film morphology.Therefore, employing is stirred at a slow speed or is not stirred and be advisable in the electrophoretic deposition thin-film process.
Interpole gap need be controlled in the proper range during electrophoresis, guarantees that again workpiece does not contact with pole plate.If interpole gap is too little, electrode resistance is low, then produces big electric current, and coatingsurface is coarse, pin hole occurs, and in uneven thickness; If interpole gap is too big, electrophoretic deposition efficient step-down then.
Then the thickness of electrophoretic deposition layer is also inhomogeneous when two electrodes are not parallel, and the local deposit thickness that distance is relatively little is big.Therefore two electrodes should be kept and parallelly make the electric force lines distribution between two electrodes even, and are even with the thickness that guarantees the electrophoretic deposition layer.Adopt the profiling electrode, each surface of assurance and workpiece is equidistant, obtains the uniform electrophoretic deposition layer of thickness, avoids settled layer to produce fringing effect.
Enamel particles of powder degree has a significant impact electrophoresis process, and particle is too little to cause the coating porous easily, because particle becomes column to pile up in deposition process, is mingled with a large amount of pores and influences coating quality easilier between the fine particle.Particle is excessive to be not easy to form steady suspension, and the coating that obtains is more coarse, and larger particles is difficult for fusing in the sintering process, has a strong impact on coating smooth finish and other performance.
After add the thing composition electrophoresis process had material impact, can reduce the viscosity of electrophoresis liquid among the present invention as suspension agent with the rare earth oxide substitute for clay, strengthen mobile, thereby make the porosity of the easier outflow reduction of the gas coating in the swimming liquid, coating oxidation-resistance, non-corrosibility and other mechanical property are all had good influence.
In sum, good electrophoretic deposition layer be obtained, the mutual relationship between above-mentioned each influence factor must be coordinated.
The present invention adopts the surfacecti proteon of enamel coating high-temperature titanium alloy, different with common enamel coating, electrophoresis presets the glaze layer and realizes thin layerization, and thickness is even, thereby avoid hyperoxia ground infiltration titanium alloy substrate in the porcelain glaze coating sintering process, cause the mechanical property of matrix alloy to descend significantly.The electrophoretic deposition process that is adopted can guarantee that the glazing composition of layer does not have depositional phenomenon according to qualifications, thereby the corrosion resistance of assurance enamel coating excellence reaches and the Performance Match of high-temperature titanium alloy.The process for protecting surface of high-temperature titanium alloy of the present invention, be applicable to the part of multiple shape, it is particularly suitable to be difficult to situation competent and that powder using efficiency is low for tubulose, spraying glazing process such as netted, has porcelain glaze powder utilization ratio height, facility investment is little, the characteristics that the technology cost is low.
Description of drawings:
Fig. 1 is the electrophoretic deposition process synoptic diagram;
Fig. 2 is the relation of reactive force and distance between particle in the electrophoresis liquid;
Fig. 3 is the relation curve between particulate interphase interaction energy (E) and its distance (D);
Fig. 4 is an electrophoretic deposition enamel layer photo under the thick situation of powder particle;
Fig. 5 is the enamel coating that contains a large amount of pores;
Fig. 6 is CeO
2Content is to the influence of enamel coating surfaceness;
Fig. 7 is rare earth enamel coating and the QBSD of basal body interface place intensified image;
Fig. 8 is common enamel coating surfaces A FM three-dimensional appearance;
Fig. 9 is a rare earth enamel coating surfaces A FM three-dimensional appearance;
Figure 10 organizes SEM QBSD picture for the rare earth enamel layer;
Figure 11 is common enamel coating wearing and tearing sample surfaces polishing scratch SEM pattern;
Figure 12 is rare earth enamel coating wearing and tearing sample surfaces polishing scratch SEM pattern;
Figure 13 is the influence to deposition quality of powder slurry concentration and time;
Figure 14 is the influence to deposition quality of voltage and time;
Figure 15 be the weightening finish curve of electrophoretic deposition when different voltage (c=150g/L, t=4s);
Figure 16 be the electrophoresis process sample over time curve (c=150g/L, U=20v).
Embodiment:
Embodiment 1
Powder proportioning: Al
2O
36.5, ZrO
24.2 ZnO 5.3, B
2O
34.3 CaO 3.8, Na
2O 1.9, CeO
2-2.0, Mg (NO
3)
25.6, ZrSiO
415.8, Na
2B
4O
78.0, SiO
2And other impurity surplus.
The powder of described proportioning is adopted the dehydrated alcohol wet ball grinding in planetary ball mill, the mode that rare earth oxide adopts mill to add, concentration is 485g/L, rotating speed is 325r/min, the powder slurry accounts for the 50%Wt of ball mill loading packet, big ball in the mechanical milling process: bead: middle ball=1: 3: 5 mass ratio, ball milling 200 hours.
Electrophoresis precoating enamel coating, electrophoretic voltage 23V; Depositing time 4s; Interpole gap 2.5cm does not stir;
Sintering: 850 ℃ of temperature, soaking time 25min.
Powder particles presets the influence of enamel layer quality to electrophoresis.
Under the condition of above-mentioned powder proportioning, electrophoretic deposition process has strict requirement to the granularity of powder.Powder particle size will influence the quality of electrophoretic deposition layer greater than 400nm, and the electrophoretic deposition enamel layer easily cracks, as shown in Figure 4.This defective that presets enamel layer is difficult to remedy by the enamel coating sintering process, thereby the performance of enamel coating is produced adverse influence; And powder particles is too small, the easy shutoff of gas that electrophoretic deposition process produces is in enamel layer, enamel coating behind the sintering easily produces pore, as shown in Figure 5, thereby the performance to coating produces adverse influence, thereby powder particles is advisable with 150-350nm, like this in the enamel sintering process, the loose electrophoretic deposition layer that is made of homodisperse solid frit particles can be converted into softening plastic state or liquid form at short notice, coat-thickness reduces, density increases, and has formed continuous even and fine and close enamel coating.
Powder proportioning: CeO
2Add-on be 1.0～2.0%, other is identical with embodiment 1.
The powder of described proportioning is adopted the dehydrated alcohol wet ball grinding in planetary ball mill, the mode that rare earth oxide adopts mill to add, concentration is 485g/L, rotating speed is 325r/min, the powder slurry accounts for the 50%Wt of ball mill loading packet, big ball in the mechanical milling process: bead: middle ball=1: 3: 5 mass ratio, ball milling 300 hours.
Electrophoresis precoating enamel coating, electrophoretic voltage 23V; Depositing time 4s; Interpole gap 2.5cm does not stir;
Sintering: 850 ℃ of temperature, soaking time 25min.
Mill adds the influence of rare earth oxide to the enamel coating surfaceness.
This invention relates to rare earth oxide CeO
2Influence to sintering enamelled coatingsurface roughness.Fig. 6 adds CeO for mill
2Content is to the influence of the surfaceness of enamel coating, as can be seen, and CeO
2Add-on be advisable CeO with 1.0～2.0%
2The coatingsurface roughness is with CeO when being lower than 1.0%Wt
2The increase of content and reduce CeO
2Content is higher than in the 2.0%Wt sintering process that the enamel film forming is too fast, and sintering process enamel coating film forming is too fast, and surfaceness increases.
Powder proportioning: Al
2O
38.0, ZrO
23.0 ZnO 6.0, B
2O
33.5 CaO 2.8, Na
2O 2.0, CeO
21.5, Mg (NO
3)
24.1, ZrSiO
414.0, Na
2B
4O
76.3, SiO
2And other impurity surplus.
The powder of described proportioning is adopted the dehydrated alcohol wet ball grinding in planetary ball mill, the mode that rare earth oxide adopts mill to add, concentration is 500g/L, rotating speed is 300r/min, the powder slurry accounts for the 50%Wt% of ball mill loading packet, big ball in the mechanical milling process: bead: middle ball=1: 2.8: 5.2 mass ratio, ball milling 200 hours.
Electrophoresis precoating enamel coating, electrophoretic voltage 23V; Depositing time 4s; Interpole gap 2.5cm does not stir;
Sintering: 850 ℃ of temperature, soaking time 25min.
Different with common enamel coating, in powder of the present invention, added multiple metallic salt additive, as Mg (NO
3)
2, Na
2B
4O
7, ZrSiO
4These materials are when improving electrophoresis liquid suspension, electroconductibility, the bonding strength that improves enamel coating and basal body interface has been played great effect, Fig. 7 is electrophoresis enamel coating of the present invention and the QBSD of basal body interface place intensified image, as can be seen, some tiny spherical reactive material are appearring at the interface, effective mutual diffusion has taken place in component and matrix element that enamel coating is described, initiating chamical reaction, can improve the bonding strength at interface greatly like this, and this situation is not observed in common enamel coating.
Embodiment 4
Powder proportioning: Al
2O
36.5, ZrO
24.2 ZnO 5.3, B
2O
34.3 CaO 3.8, Na2O 1.9, CeO
2-2.0, Mg (NO
3)
25.6, ZrSiO
415.8, Na
2B
4O
78.0, SiO
2And other impurity surplus.
The powder of described proportioning is adopted the dehydrated alcohol wet ball grinding in planetary ball mill, the mode that rare earth oxide adopts mill to add, concentration is 500g/L, rotating speed is 300r/min, the powder slurry accounts for the 45%Wt of ball mill loading packet, big ball in the mechanical milling process: bead: middle ball=1: 2.8: 4.8 mass ratio.
Electrophoresis precoating enamel coating, electrophoretic voltage 23V; Depositing time 4s; Interpole gap 2.5cm does not stir;
Sintering: 850 ℃ of temperature, soaking time 25min.
The ball milling time is to the influence of powder electrophoresis process.
What the present invention relates to is a kind of electrophoresis precoating technology of nanopowder enamel coating.Different with common spraying and dip-coating glazing process, ball mill mixing is bigger to forming uniform and stable electrophoresis enamel settled layer influence, because the nanopowder surface tension is bigger, very easily reunite, when the ball milling time is lower than 100h, the batch mixing inequality, can cause enamel coating inner oxide skewness or oxide buildup behind the sintering to become blocky situation, this brings adverse influence to anti-oxidant, the corrosion and the polishing machine that improve enamel coating, test was found the ball milling time above 300 hours, and is little to the tissue and the performance impact of electrophoretic deposition process and enamel coating.
Embodiment 5
Powder proportioning: Al
2O
38.5, ZrO
23.5 ZnO 6.8, B
2O
33.9 CaO 2.5, Na
2O 2.5, Mg (NO
3)
24.3, ZrSiO
414.2, Na
2B
4O
76.7, SiO
2And other impurity surplus.Add or do not add 1.5 CeO
2
The powder of described proportioning is adopted the dehydrated alcohol wet ball grinding in planetary ball mill, the mode that rare earth oxide adopts mill to add, concentration is 500g/L, rotating speed is 300r/min, the powder slurry accounts for the 45%Wt of ball mill loading packet, big ball in the mechanical milling process: bead: middle ball=1: 2.8: 4.8 mass ratio, ball milling 200 hours.
Electrophoresis precoating enamel coating, electrophoretic voltage 23V; Depositing time 4s; Interpole gap 2.5cm does not stir;
Sintering: 850 ℃ of temperature, soaking time 25min.
By investigating rare earth oxide the influence of enamel coating tissue and polishing machine is found, proper amount of rare-earth is very big to tissue topography, structure and the polishing machine influence of enamel coating, Fig. 8,9 is respectively common enamel coating and contains 1.5% rare earth oxide enamel coating AFM three-dimensional appearance, add the proper amount of rare-earth oxide compound as can be seen, can make the obvious refinement of tissue of enamel coating, and the SEM structure observation is found, occurred many starlike phases (as shown in figure 10) in this coating structure, composition analysis shows that it is for being rich in the Ce phase.This is because CeO
2Has very strong oxidisability, CeO
2In enamel coating, can exist, promptly with two kinds of valence state forms
, Ce
4+Have photosensitive and sensitive characteristic, in the enamel coating sintering process, the receptor that awards that it very easily becomes valence electron makes that the energy in the enamel changes, and causes spontaneous nucleation, thereby causes crystallization activation energy to reduce, and causes the enamel coating grain refining, dense structure.
The frictional coefficient and the wear rate of table 1 base material Ti60 alloy and enamel coating
| Material | Frictional coefficient | Wear rate/10 -2mm 3·h -1 |
| The common enamel coating rare earth of titanium alloy base material enamel coating | 0.67 0.91 0.71 | 32.7 4.59 2.81 |
Table 1 is Ti60 alloy substrate material, common enamel coating and frictional coefficient, wear rate and the relative wear resistance that contains the rare earth oxide enamel coating.As can be seen, the wear rate of enamel coating is starkly lower than the Ti60 alloy base material, and its relative wear resistance is 7.12.This mainly is owing to contain a large amount of oxide compounds in the enamel coating, specimen surface hardness is up to 3065Hv, hardness near near the coating titanium alloy substrate interface region is about 2195Hv, and Ti60 alloy substrate hardness only is 400～500Hv, enamel coating makes that Ti60 alloy base material surface hardness obtains to improve greatly, thereby helps improving its surface abrasion resistance energy.It can also be seen that from table 1, contain CeO
2The wear rate of enamel coating is lower, and its relative wear resistance is 11.64, is 1.64 times of common enamel coating.But detecting, experiment finds CeO
2Hardness to enamel coating does not produce tangible influence, and the hardness of coating fluctuates in 2 202～3 098Hv scopes substantially, and the minimizing of its abrasion loss mainly is to pass through CeO
2Tissue topography, the structure of improving enamel coating inside realize.Measuring friction coefficient is the result show, common enamel coating is under the test conditions of frictional wear, and coating shows bigger frictional coefficient, and the easier fragility that becomes of bubble in the coating and oversize particle is peeled off the source, cause crack propagation in the coating abrasion process, frictional coefficient increases.Contain CeO
2Enamel coating because the coating structure densification, crystal grain is tiny, makes itself and friction pair show as lower frictional coefficient as the time spent, thereby plays useful effect for the wear resistance of improving coating.
SEM observes discovery, the following recess of common enamel coating polishing scratch is sharp tooth, and polishing scratch both sides size is irregular, show and the hole of peeling off that varies in size occurred, this mainly is because the enamel coating wear mechanism peels off based on fragility, with the carrying out of skimming wear, causes that to peel off pit edge irregular, in peeling off the hole, vertically, laterally all form crack propagation with broken, and crackle connection phenomenon takes place.The adding of rare earth oxide has improved enamel coating interior tissue pattern, as can be seen from the figure, contain the rare earth oxide enamel coating owing to the coating structure refinement, toughness improves, the more common enamel coating of sample surfaces polishing scratch is Paint Gloss, shows that the crack propagation tendency reduces to some extent.
Figure 11,12 is respectively two kinds of enamel coating sample worn area surface topographies, and under same magnification situation, common enamel coating surface polishing scratch is obviously coarse.SEM observes discovery, common enamel coating fragility in wear process is peeled off more serious, polishing scratch surface local zone pattern is rock hole shape, the fragility that the bony shape of its tooth distributes is easier mutually peels off in wear process, and along with the carrying out of skimming wear, peel off the pit edge form and become more and more irregular, and the hole is inner to be formed a large amount of crack propagation and peel off with fragility peeling off, and crackle connection phenomenon takes place.Figure 12 is the polishing scratch surface topography that contains the rare earth enamel coating, eroded area inside is the cotton-shaped distribution of group as can be seen, the hard comparatively disperse that distributes mutually, and hard particles and enamel coating matrix bond are good, the bony shape structure of the tooth of worn area obviously reduces, and more is easy to generate sliding friction like this in wear process.Group's flocculent structure in the coating provides toughness plasticity relatively preferably for the top layer, be subjected to stress on the top layer, when particularly being hit, can be within the specific limits reduce the impaired degree in top layer, then show as the minimizing of absolute abrasion loss on the macroscopic view in the mode of recoverable deformation.
Frictional wear experiment shows that the wear mechanism of enamel coating is that fragility is peeled off, and the adding of rare earth oxide has improved the toughness of enamel coating, reduces the tearing tendency in the coating abrasion process.Compare with common enamel coating, the frictional coefficient of rare earth enamel coating has descended 22%, and relative wear resistance improves 1.64 times, thereby has improved the friction resistant polishing machine of enamel coating effectively.
Embodiment 6
With embodiment 1 powder is that raw material mixes with dehydrated alcohol, prepares electrophoresis liquid powder slurry, carries out prerunning and apply on the high-temperature titanium alloy matrix.Parameter such as concentration and electrophoretic voltage has considerable influence to electrophoretic velocity, experimental result such as Figure 13, shown in Figure 14, as seen, at pulp density less than 100g/L or voltage during less than 15V, W and t are linear substantially, explanation at powder slurry concentration or voltage hour, the electrophoretic deposition process rate controlling step is the migration of electrolysis reaction and reactant and product, and the electrodeposition rate controlled step is an electrophoretic migration when pulp density C 〉=100g/L or voltage U 〉=15V.
Electrophoretic deposition speed with the curved line relation of voltage change as shown in figure 15.As seen from Figure 15, under constant condition of constant time, with the increase of voltage, the weightening finish of sample unit surface also increases gradually.This is because voltage is big more, and strength of electric field is just big more under the same interpole gap condition, and then the motivating force as electrophoretic migration is just big more, and therefore the enamel powdered frit of electrophoretic deposition is also just many more in the identical time.
Table 2 voltage is to the influence of electrophoretic deposition coating quality
(powder slurry concentration is 150g/L to voltage coatingsurface quality, electrophoresis
(V) time is 4s)
10 coatings are thinner, do not cover matrix fully
15 surfaces are more smooth, but coating is thinner
20 surfaces are more smooth, do not have obvious mass defect
25 coatingsurfaces are smooth, and thickness is even
30 coatingsurface unfairnesses, and a large amount of pin holes appear
But the surface quality of coating is not that voltage is the bigger the better as can be known behind the constant time 4s voltage change electrophoretic deposition that is provided by table 2.Overtension when the same pole spacing, can produce big electric current, then causes coatingsurface coarse, defectives such as pin hole occur, and in uneven thickness.In fact during electrophoresis, have the operating voltage of a maximum, surpass this voltage, the coating deposited film is with breakdown, and electric current rises again, and this voltage is called voltage breakdown.Therefore, want suitable regulating voltage size in the electrophoresis experiment, to obtain good deposited coatings.
Powder slurry concentration is 150g/L, and when electrophoretic voltage was 20V, the time was as shown in table 3 to the influence of electrophoretic deposition layer quality, and its kinetic curve as shown in figure 16.
Table 3 time is to the influence of electrophoretic deposition coating quality
(powder slurry concentration is 150g/L to time coatingsurface quality, voltage
(s) be 20V)
3 surfaces are even, but coating is thinner
4 coatingsurfaces are smooth, and thickness is even
5 coatingsurfaces are even, but indivedual pin holes appear in the edge
6 coatingsurfaces have pin hole, and crackle occurs
The too thick crackle that occurs of 7 surface irregularities, coating, and
More pin hole is arranged
Analyze as can be known, in the increase in time of the starting stage of galvanic deposit, the sample weightening finish is very fast, the later prolongation of 6s along with the time, weightening finish is tending towards slow, this is because along with the settled layer thickening, resistance obviously increases, and make electrophoretic current density reduce (as shown in figure 14) gradually, so electrophoretic velocity reduces gradually, thereby electrophoretic deposition speed slows down gradually, so specimen surface unit surface weightening finish slows down, and along with the prolongation of time, the surface quality of deposited coatings descends, therefore, should choose suitable depositing time in the experiment.
By above experimental result as can be known, the electrophoretic deposition experimentation is subjected to influence of various factors.
Claims (7)
1, a kind of process for protecting surface of high-temperature titanium alloy is characterized in that: at surface preparation one deck high-temperature oxidation resistant enamel coating of high-temperature titanium alloy;
Coat-thickness is: 15-70 μ m;
Chemical constitution is: Al:2.6-4.2; Si:20.7-29.8; Ca:1.9-2.4; Zn:1.2-2.0; Zr:2.6-3.7; Na:0.4-1.1; Mg:0.4-0.9; Ce:0.6-1.2; O and impurity surplus.
2,, it is characterized in that the preparation technology of described high-temperature oxidation resistant enamel coating is according to the process for protecting surface of the described high-temperature titanium alloy of claim 1:
---electrophoresis precoating enamel coating,
The chemical constitution of enamel powder is that weight percent is:
Al
2O
3 6.5～10.2；
ZrO
2 2.7～4.2；
ZnO 5.3～8.9；
B
2O
3 2.7～4.3；
CaO 1.9～3.8；
Na
2O 1.9～3.6；
Rare earth oxide 1.0-2.0;
Mg(NO
3)
2 2.0～5.6；
ZrSiO
4 12.2～15.8；
Na
2B
4O
7 5.2～8.0
SiO
2And other impurity surplus;
With ethanol is that dispersion agent prepares slip, pulp density 150-350g/L;
Electrophoretic voltage 20-25V;
Depositing time 3-5s;
Interpole gap 2-3cm gently stirs or does not stir;
---sintering:
Temperature 850-880 ℃, soaking time 20-30min.
3, according to the process for protecting surface of the described high-temperature titanium alloy of claim 2, it is characterized in that, in the enamel powder:
Al
2O
3 2.1-3.5。
4, according to the process for protecting surface of the described high-temperature titanium alloy of claim 2, it is characterized in that, in the enamel powder:
Mg(NO
3)
2 2.0-3.6。
5, state the process for protecting surface of high-temperature titanium alloy according to claim 2, it is characterized in that, in the enamel powder:
ZrSiO
4 12.0-14.5。
According to the process for protecting surface of the described high-temperature titanium alloy of claim 2, it is characterized in that 6, in the enamel powder: rare earth oxide is CeO
2
7, according to the described enamel powder for electrophoresis coating of claim 2, it is characterized in that: powder particles is at 150-350nm.
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| CN101497496B (en) * | 2008-02-02 | 2011-06-15 | 比亚迪股份有限公司 | Porcelain enamel glaze composition, film coating material and preparation thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US4892847A (en) * | 1988-06-13 | 1990-01-09 | Ciba-Geigy Corporation | Lead-free glass frit compositions |
| CN1142113C (en) * | 1998-09-28 | 2004-03-17 | 中国科学院金属腐蚀与防护研究所 | High-temperature protection technology for titanium alloy and titanium-aluminum intermetallic compound |
| CN1207441C (en) * | 2002-06-14 | 2005-06-22 | 中国科学院金属研究所 | Method of risisting high-temp. oxidation and heat corrosion for high-temp. alloy |
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2005
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